Re: LOR kqueue / sleep mtxpool for LOR list

On Tue, 18 Dec 2007, Ed Maste wrote:

> On Tue, Dec 18, 2007 at 10:20:21AM -1000, Jeff Roberson wrote:
>
>> On Tue, 18 Dec 2007, Ed Maste wrote:
>>
>>> I just saw this LOR during startup of an application while testing
>>> 8-CURRENT on a dev box.  I've done no investigation yet.
>>>
>>> FreeBSD TPC-D13-08.phaedrus 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Mon Dec 17
>>> 16:27:54 EST 2007
>>> emaste_at_bsd-build3.phaedrus:/d2/emaste/HEAD/obj/d2/emaste/HEAD/src/sys/GENERIC  i386
>>>
>>> lock order reversal:
>>> 1st 0xc42b7580 kqueue (kqueue) _at_
>>> /d2/emaste/HEAD/src/sys/kern/kern_event.c:1397
>>> 2nd 0xc3ece8e0 sleep mtxpool (sleep mtxpool) _at_
>>> /d2/emaste/HEAD/src/sys/kern/sys_generic.c:1255
>>> [...]
>>
>> Thanks, this is interesting.  The mtxpool should always be the leaf.  The
>> opposite order is the bug.  Can you add them to the static order list and
>> tell me where the reverse order is observed?
>
> After adding it to the list this is what I got:

Ah this is sort of ridiculous.  Thanks.  I will fix this within a week or 
two.

Jeff

>
> Mounting NFS file systems:lock order reversal:
> 1st 0xc3ece280 sleep mtxpool (sleep mtxpool) _at_ /d2/emaste/HEAD/src/sys/kern/kern_event.c:993
> 2nd 0xc4320d80 kqueue (kqueue) _at_ /d2/emaste/HEAD/src/sys/kern/kern_event.c:1001
> KDB: stack backtrace:
> db_trace_self_wrapper(c0b08831,e683daac,c079cabe,c0b0ada3,c4320d80,...) at db_trace_self_wrapper+0x26
> kdb_backtrace(c0b0ada3,c4320d80,c0b01d5d,c0b01d5d,c0b01a4d,...) at kdb_backtrace+0x29
> witness_checkorder(c4320d80,9,c0b01a4d,3e9,7db,...) at witness_checkorder+0x6de
> _mtx_lock_flags(c4320d80,0,c0b01a4d,3e9,0,...) at _mtx_lock_flags+0xbc
> kqueue_acquire(c445eaa0,4,e683db5c,c0b04436,f0,...) at kqueue_acquire+0x72
> kern_kevent(c445eaa0,4,1,1,e683dc60,...) at kern_kevent+0x47
> kevent(c445eaa0,e683dcfc,18,c0b0bacf,c0bb92e8,...) at kevent+0x19b
> syscall(e683dd38) at syscall+0x2b3
> Xint0x80_syscall() at Xint0x80_syscall+0x20
> --- syscall (363, FreeBSD ELF32, kevent), eip = 0x2813dafb, esp = 0xbfbfd28c, ebp = 0xbfbfd388 ---
>
> -Ed
>